The present program is concerned with the neuroanatomical sites involved in and the physiological processes concerned with the discharge of pituitary luteinizing (LH) and follicle stimulating hormone (FSH). It has been observed that the preoptic area (POA) of the brain is intimately concerned with the ovulatory discharge of LH. Furthermore, at the time of LH release a concomitant discharge of FSH occurs. Portions of the current investigation are determining whether or not specific but separate central nervous system regions are responsible for FSH release. Preliminary results have demonstrated a selective release of FSH upon electrochemical stimulation of the dorsal anterior hypothalamus. The interrelationships which exist amongst this region, the POA and the terminal infundibular regions are being evaluated. As well, the role of the sex steroids (estrogen and progesterone) in modifying CNS controls, the temporal patterns and concentrations in plasma in relationship to pituitary GTH release also are being examined. Of particular concern are those levels of steroids which exert initial positive feedback actions on the CNS-pituitary unit but at higher or more prolonged concentrations have negative feedback effects. Finally, the patterns and concentration changes in the biogenic amines and their interrelationships to the changes in luteinizing hormone-releasing hormone (LH-RH) are being investigated. Of particular interest are the types of alterations produced in these neurotransmitters by stimuli which precipitate the ovulatory discharge of the gonadotropic hormones.